I don't know about your State specifically, but in mine and I think most others the taxes are between the buyer and the Government with jusrisdiction. The seller typically isn't involved in that transaction.

Income taxes, of course, are another matter, if that's any concern to you...

The thing I worry about most as a seller in a private transaction is getting myself off the hook for any responsibility for the RV once it's left my hands...some buyers aren't exactly lickety-split about transferring Title, and it's not nice to get notices of parking infractions or worse months down the road because they "forgot" to transfer it at all!

In my State there's a form attached to every vehicle Title called "release from liability". or some such language. The seller is to fill that out and turn it in at the time of the sale, and the buyer then has "X" number of days to transfer Title to their name. But even if they fail to do so, by notifying the State of the transaction details, the seller is released from any/all responsibility for the vehicle.

I think this to be the next most important thing to do when selling a vehicle/RV, other than cashing the check, of course!

" Not every mind that wanders is lost. " With apologies toJ.R.R. Tolkien

like any vehicle take the new buyer along with the paper work to the dmv and change over the title so you are not responsible for it any more. every thing I have sold I take in and get it changed before he gets the vehicle. if he does go in with me then he doesn't get the vehicle.

When you fill out the bill of sale you put on there "sold as is condition". I was in a cout of law on an issue after selling an item. This statement held up in the courts. I was relieved of any cost for repairs.

I'd add to the trip to the DMV, even if the buyer is out-of-state, they can get a temporary "in-transit" permit to get it home, NEVER let them take your plates. And second, make sure you have their money. Not just a check, never a money order, never a check for more than the purchase price where you give them money back. If they insist on using a check, call their bank and verify the account, go to your bank and present the check for payment(sometimes called a demand payment) and get a cashier's check from your bank and still make the buyer wait two weeks to pick up their rig.That makes sure you get paid.

Great tips from woodgeezer - even our Dealer kept the title of our rig until our checks cleared their bank. Cash or certified bank check - if a certified bank check call the bank to verify it is real. too many scams out there for sure.

Such transactions are VERY state law specific.
For instance, in some states the license plates stay with the vehicle forever.
In some states the license plates belong to the vehicle owner, and must be removed when the vehicle is sold. Montana is one such state.
In some states the title is held by the lien holder.
In some states, the title is held by the registered owner. Montana is one such state.
In some states, a Bill Of Sale is necessary, to show the purchase price for tax purposes. In some states, they charge the tax on some magic number that only the DMV knows, in other states they have a "book value" for taxation, and some states there is no sales (or use) tax.
Now, OP, having said all that, what does YOUR state require? THAT is what you need to know. Contact the appropriate authorities in YOUR state for answers.